8 DR; F E. BEDDARD ON 
budding scolices. They generally appear to be empty ; but traces 
of an apparently coagulated fluid are to be observed after deep 
staining with hematoxylin. They have invariably well defined 
edges, and thus cannot be confused with the true bladder-cavity 
as I assume it to be. In the section which is represented in text- 
figure 2, these larger spaces with their well defined walls are 
plainly to be distinguished from the space lettered A in that 
figure with its lining of membrane and outer coat of glandular 
cells. The difference is most striking and is accompanied also by 
a difference in size which is apparent in the same drawing. Iam 
not, however, convinced that there is a real difference. For some 
of the cavities in question show distinctly a layer of cells im- 
mediately outside of the cavity, and traces of a thin membrane 
within that are to be noted. An expansion of such a tube as is 
represented in A of text-figures 2 & 3 might well lead to such 
appearances by a stretching of the lining membrane and by the 
pulling apart of a close layer of cells. On the other hand, some of 
the cavities lettered C (see text-fig. 4) are undoubtedly without a 
distinct layer of cells around them. But here again the continued 
expansion and perhaps the degeneration of the cells, if they are 
concerned with the production of the fluid within the cavities, 
may have produced such a result. ‘As I have no younger stages 
than that of which I am now giving the description, the matter 
does not as I think admit of a more definite expression of opinion. 
The most careful examination has not shown any connection 
between these cavities ; they are quite isolated as far as I could 
make out; and if connections occur they cannot be abundant. 
Nor were there any orifices on to the exterior to be observed. I © 
followed out through a series of sections the course of more than 
one of the cavities and could find no outlet from their interior 
in any direction. ‘There is, however, some evidence, though not 
very strong, that they are formed out of the original bladder- 
cavity. When the latter is carefully followed up to its anterior 
end (as I have called it for reasons given), the cavity is seen to 
acquire walls like those which surround the numerous cavities 
lying beyond itsanterior end. It ends in fact in what looks very 
much like one of the cavities lettered C. But this cavity does 
not end in the parenchyma or in connection with one or 
more of the rounded spaces just described. It is seen to lie 
within one of the latter cavities and to end in it without 
opening into it. But we may have here the last remaining 
vestige of such a connection as has been suggested. Here 
again the absence of younger stages forbids a more definite 
statement. 
The last series of cavities are those lettered d. These are 
undoubtedly the tubes of the water-vascular system and are 
peripheral in position. It is, however, to be noted that these 
tubes and spaces do not invariably, though they do generally, lie 
outside of the cavities belonging to the category C. The water- 
vascular system consists partly of irregular spaces of a tubula 
